Ignition distributor



I Aug. 2, 1960 J, KlTTLER 'ETAL I 2,947,297

Filed Aug. 29, 1958 IGNITION DISTRIBUTOR 4 Sheets-Sheet 1 mvsmons A4. Ta/v J K1774 ER; 1 /llzz w/v [fun/2 &

K44 MS Jbbwsom ATTORNEY Aug. 2., 1960 M. J. KITTLER ETAL IGNITION DISTRIBUTOR Filed Aug. 29, 1958 4 Sheets-Sheet 2 INVENTORS M/L ro/v JA Filed Aug. 29, 1958 r M. J. KITTLER ETA!- IGNITION DISTRIBUTOR 4 Sheets-Sheet 3 Aug. 2, 1960 Filed Aug. 29, 1958 SIMFT M. J. KITTLER ETAL IGNITION DISTRIBUTOR 4 Sheets-Sheet 4 ATI'OE/YEX United States Patent IGNITION DISTRIBUTOR Milton J. Kittler and Melvin F. Sterner, Bloomfield Hills, and Kalin S. Johnson, Northville, Mich., assignors to Holley Carburetor Company, Van Dyke, Mich, a corporation of Michigan Filed Aug. 29, 1958, Ser. No. 757,965

14 Claims. (Cl. 123-117) This-invention relates generally to ignition distributors, and more specifically to those distributors which are responsive to variations in engine speed and load.

Many designs of distributors have been proposed and tried wherein centrifugal and vacuum forces are used to regulate the timing advance and/or retard of the distributor. However, none of these have been able to combine all of the desirable features, such as (1) flexibility of calibration, (2) elimination of vacuum leakage, (3) rugged advance mechanism, (4) stationary breaker plate and (5) perfect rotor registry, into a workable embodiment.

Accordingly, it is an object of this invention to provide means whereby all of the above features can be included in an ignition distributor.

Other objects and advantages of the invention will become apparent when reference is made-to the following specification and illustrations, wherein:

Figure 1 is an elevational view of an ignition distributor constructed in accordance with the invention, with portions of the distributor housing being cut away and in cross-section. Figure 1 includes a schematic illustration of the engine.

Figure 2 is a top plan view of the distributor shown in Figure l, with the cap and rotor removed.

Figure 3 is a cross-sectional View of the distributor taken substantially on the plane of line 3--3 of Figure 1 and looking in the direction of the arrows.

Figure 4 is also a cross-sectional view of the distributor taken substantially on the plane of line 33 of Figure 1 looking in the direction of the arrows; Figure 4 dilfers from Figure 3 in that some, of the elements shown in Figure 3 have been removed.

Figures 5, 6, and 7 are perspective views of some of the elements included in the preferred embodiment of the invention.

Figure 8 is a cross-sectional view taken substantially on the plane of line 8-8 of Figure 7 and looking in the direction of the arrows.

Figure 9 is a fragmentary view illustrating the pneumatic conduitry employed in the invention.

Figure 10 is a schematic representation of the lever arms and forces affecting the operation of the advance mechanism embodying the invention.

Referring now in greater detail to the drawings, Figure 1 illustrates an ignition distributor 10 which communicates by means of suitable conduitry schematically illustrated at 12' with a port 14 in the carburetor 16. The carburetor 16 is located on manifold 18 in such a manner so as to deliver a combustible mixture, the flow of which is controlled by the throttle valve 20, to the individual intake ports of the cylinders located in engine 22.

The distributor 10 comprises a housing 24 including a depending reduced portion 26 having an opening 28 theretbrough for the reception of a driving shaft 30. The upper end of the cup-shaped housing 24 is generally closed by a breaker plate 32 on which is mounted the breaker arm assembly 34, which includes a cam engaging ice portion 36 engageable by the rotating cam 38 to effect make and break of the circuit at the contacts indicated at 40 (Figure 2). The cam 38 is fixedly secured to a tubular shaft 42 which is rotatable with the shaft 30 in its normal operation, but which is also angularly adjustable relative thereto to advance or retard the spark timing.

An insulated rotor 44', having a spring-like electrical contact 46 thereon, is secured to the upper portion of tubular shaft 42 and is adapted to be rotated thereby normally in accordance with engine speed. Contact 46, which is continually biased against the ignition coil input terminal 48 of the distributor cap 49, is adapted to sequentially traverse the output terminals :50 of cap 49 (of which only one is shown) and is so positioned that the two are in juxtaposition whenever the electrical discharge occurs.

Shaft 30 has a conduit 52 formed therein which communicates between the vacuum responsive advance mechanism, to be described later, and the conduitry 12 by means of a radially formed conduit 54, chamber 56 and the horizontal conduit 58. Chamber 56, formed generally by bushing 60 and depending portion 26, has seals 62 and 64 therein which are displaced by suitable retainers 66 and a spring member 68. The seals are provided in order to prevent any possible vacuum leakage between the shaft 30 and any coacting elements such as portion 26. The shaft 30 is of course driven in accordance with engine speed as by means of gear 70.

Figure 3 illustrates in plan view the general arrangement of the advance mechanism. A base plate 72, which is rigidly secured to shaft 30 through a bushing member 74 (see Figure 1 also), carries diametrically opposed pins 76 and 78 which are fixed therein so as to be parallel to shaft 38. These pins 76 and 78 provide pivoted supports for the advance devices indicated generally at 80 and 82'. It may be well to note at this time that the fact that different numerals are used to identify apparently identical elements should not be construed to imply that the elements are different. For reasons which will become obvious later in the specification, individual elements, regardless of whether or not they are identical or similar to others, are identified With their own specific reference numbers.

The advance devices 80 and 82 have extending arm portions '84 and 86, respectively, which in turn are pivotably mounted at 76 and 78 by means of sleeve members 88 and 90. A cam plate 92, which is rigidly secured to the lower portion of tubular shaft 42, is connected to the advance devices, as by means of downwardly extending pins 94 and 96 which are secured to the plate 92. The motion transmitting links 98 and 100 extending from the devices 80 and 82 are adapted to coact with pins 94 and 96, as by means of sleeve portions 102 (see Figure 4 also), in order to ultimately determine the degree of advance or retard of cam 38 (Figure l).

Figure 4 is a sectional plan view similar to Figure 3 except that cam plate 92, tubular shaft 42, the advance device 80 and pin 76 have been removed for purposes of clarification. A curve plate 104, having a collar portion 106, is mounted on shaft 30 in such a manner so as to have freedom of angular movement with respect to said shaft. Calibrating springs 108 and 110 are secured at one end to adjustable tabs 112 and 114; the other ends of the springs are fastened to arms 116 and 118 of the curve plate 104-. The curve plate 104 also has another pair of diametrically opposed arms 120 and 122 which are adapted to be continually in contact with levers 124 and 126. The contacting surfaces 128 and 130 (Fig. 6)

of arms 120 and 122 are developed so that the advance arm 84 near the pivoted end thereof. A projection 136v extends from the under side of arm 84 and serves to hold an adapter member 140 which is in effect a short conduit which communicates with conduit 12 in a manner to be later described. It should be mentioned that the advance device 80 illustrated is identical to the device 82.

Figure 8, a substantially cross-sectional view of Figure 7, illustrates the details within the advance device 80. The device 80 is generally comprised of a housing 138 which retains a diaphragm 142 therein by virtue of suitablerneans such as the rim flange portion 144. A cover plate 146 is provided in order to prevent possible damage to the diaphragm 142. An upwardly extending, internally threaded collar portion 148 is secured to the housing 138 opposite the diaphragm 142. An adjustable spring abutment 15 having'externally formed threads coacts with collar 148 and spring 152 to bias the diaphragm 142 outwardly. Axial adjustment of abutment 15% can be made by inserting suitable shims, as illustrated at 154, between itself and collar 148. Shims of course may be placed between spring 152 and abutment 150 if so desired.

' During periods of operation when the vacuum in chamber 162 is not sufficient to move diaphragm 142, the spring 152 biases the diaphragm outwardly causing the diaphragm clamp plate 156 to contact cover plate 146. The motion transmitting link 9% may be secured to the diaphragm 142 as by means of oppositely disposed plates 156 and 153.

The arm portion 54 has a conduit 160 formed therein which communicates with chamber 162, formed generally by housing 138 and diaphragm 142, by means of a port 164 in housing 133. A flexible conduit 16o, which communicates with a source of vacuum, is adapted to be externally received by conduit portions 14-0 which, in turn, communicates with conduit 160 as by a passageway 168 formed in both arm 4 and portion 135 (see Figure 7 also).

Operation 118. When the curve plate 104 is urged in this "direction, it causes the advance devices 80 and 82 to be urged in a clockwise direction'about their respective pivots 76.

and 78 by virtue of the cooperative action between arms 122 and 120 of curve plate 104 and levers 126 and 124 secured to the advance devices 80 and 82, respectively.

The advance devices will move in a clockwise direction, until the truncated portion 176 of covers 146 abut against the trailing edges of levers 124 and 126. At this time, the cam 38 (Figure 1) will have been rotated clockwise to its full retard position by virtue of tubular shaft 42, earn plate 92, and the connection between the motion transmitting links 98 and 100 and the pins 94 and 96' secured to cam plate 92. i i

As engine speed increases, the rotational speed of shaft 30 will correspondingly increase, and the weighted advance devices 80 and 82 will travel arcuately outwardly about their pivoted ends 88 and 9%. As the advance devices 80 and 82 move outwardly, the motion transmitting links 98 and 100 rotate cam plate 92 and cam 38'counterclockwise with respect to shaft 30, thereby causing an advance which is generally related to the increase in speed. The forces which restrict outward movement of the advance devices are ultimately due to the resistance offered by the tension springs 108 and 110;

In order to modulate the normal centrifugal forces of the advance devices and 82, a curve plate 104 (Figures 3 and 4) is employed. Generally speaking, the centrifugal forces of the advance devices increase as the square of the speed, and the desired result is to have displacement due to the centrifugal forces increase, at the most, in a linear fashion with respect to speed. This result is obtained by proper calibration of the curve plate 104.

Referring principally to Figure 4, it is seen that the resisting forces of the springs 10% and are transmitted to the advance devices 80 and 32 through the curve plate 104, as by means of arms 116 and 118, 'arms 120 and 122 and levers 124 and 126, which are made functionally integral with the advance. devices.

Figure 10 illustrates schematically the mechanics of the force compensating mechanism employed. As the speed of rotation about shaft 30 increases, the excessive centrifugal forces, F are overcome by the tension (F,,) of spring 108; this is accomplished by creating a greater. effective spring force through means continually changing the effective lever arms, as from points A to B to C. The principle of varying effective forces by varying intermediate lever arms is well known; however, the means by which this principle is practiced in the present invention is, a considerable improvement over that which is presently considered to be general practice. i

For purposes of illustration, let it be assumed that the elements of Figure 10 are at a condition of equilibriumwhen the arms 120 and 124 are tangent at 'pointA and that the following are true:

(1) F r centrifugal force of mass 82.

(2) L =lever arm of centrifugal force F (3) L =lever arm of arm 124.

(4) L lever arm of arm 120.

(5) F the unresolved component of the normal result ing force opposing arms 120 and 124 at point A;

(6) =force of spring 108.

(7) A =deflection of spring 108.

( 8) K =spring constant of spring 108.

(9) L =lever arm of spring force F (.10) A =movement of mass 82 corresponding to A,,.

From the above, the following relationships exist:

or since K, and L, are constants,

From the above, it is apparent that the force of spring 108 is not only a function of the centrifugal force but;

also a function of the ratio of the lever arms L and L of members 124 and 120, respectively. This ratio, which changes when L and L change in equal and opposite: amounts, can, of course, be controlled by contouring the edges 122 and 128 to any" required shape. i

When the throttle valve 20 'is opened, a sourcev of vacuum is made available at port 14 for the regulation of the cam 38 in accordance with engine vacuum. Re ferring now to Figures 1, 4, 7, 8, and 9, the vacuum is transmitted from port 14 through conduits 12, 58, 5 2, to tubular projections 172 and 174, which are pneu matically connected to flexible conduits 16,6. and 16 respectively. The. other ends of conduits 166 and 167.:

are connected to adapted members140 onarms 84 and 86 in such a manner so as to communicate with conduits 160 and chambers 162 of the advance devices 80 and 82.

Assuming now that the advance devices have been positioned in accordance with engine speed, any part throttle position will cause vacuum to be communicated to chambers 162 and accordingly move the diaphragm 142 in wardly against the force of spring 152. The maximum advance is, of course, when the diaphragm assembly abuts against the stop 150.

Referring to Figure 8, it becomes apparent that the vacuum advance is completely independent from that of the speed advance and therefore lends itself readily to a practical embodiment.

In summarizing the advantages of the invention, it can be pointed out that the curve plate 104 which controls the speed advance is interchangeable. That is, it is a loose piece which can easily be removed for replacement or recalibration without any rework of the distributor, as is required by present distributors employing a curve plate. Further, there is perfect rotor registry at all speeds even though there are independent controls for cam advance in accordance with engine speed and vacuum. Perfect rotor registry of course, refers to the fact that the rotor 44 and contact 46 are in juxtaposition to the output terminals 50 whenever an electrical discharge occurs. This result is obtained by virtue of the cam 38 being rotated by the advance mechanism instead of the breaker arm assembly, as is conventional in distributors responsive to vacuum. Perfect rotor registry provides for proper distribution of electrical discharges and prevents any misfiring or cross-firing as between any two successive output terminals as indicated at 50. In addition, the construction is one which has no vacuum leakage and at the same time exhibits a high degree of sensitivity to changes in control parameters.

Although only one embodiment has been disclosed, it is apparent that other modifications are possible without exceeding the scope of the appended claims.

What we claim as our invention is:

1. In an ignition distributorfor an internal combustion engine having an induction passage, a drive shaft adapted to be driven in accordance with engine speed, a cam member coaxial with said shaft and adapted to be angularly adjustable relative thereto, means responsive to changes of engine operating conditions for adjusting said cam member relative to said shaft, said means combining speed responsive elements and pressure responsive elements, said speed responsive elements being capable of independently adjusting said cam in response to variations in engine speed, and a floating generated calibration plate for modifying the action of said speed responsive elements, said pressure responsive elements being capable of independently adjusting said cam in response to variations in induction passage vacuum regardless of engine speed and without moving said speed responsive elements or influencing said calibration plate in any way.

2. In an ignition distributor for an internal combustion engine having an induction passage, a housing, a shaft mounted through one end of said housing for rotation therein in accordance with engine speed, a base plate mounted on said shaft and disposed normally thereto, a cam member normally rotatable with said shaft for elfecting a make and break of the ignition circuit, a cam plate rigidly secured to said cam member, a plurality of diametrically disposed pivotal suppo'rt members located within said base plate, weights pivotally mounted on siad support members and adapted to have arcuate movement in response to variations in engine speed, a plurality of springs each anchored at one end to said base plate, lever arms secured to said weights at the pivotally mounted ends, a floating curve plate mounted on said shaft and having secured thereto the other ends of said springs, said curve plate and said levers being positioned so as to be in substantial juxtaposition to each other and alwaysin contact with each other, and means connecting the free ends of said pivotally mounted weights and said cam plate for rotating said cam plate and said cam member in accordance with engine speed.

3. In an ignition distributor for an internal combustion engine having an induction passage, a housing, a shaft mounted through one end of said housing for rotation therein in accordance with engine speed, a base plate mounted on said shaft and disposed normally thereto, a cam member normally rotatable with said shaft for effecting a make and break of the ignition circuit, a cam plate rigidly secured to said cam member, a plurality of diametrically disposed pivotal support members extending from said base plate, weights pivotally mounted on said support members and adapted to have arcuate movement in response to variations in engine speed, a plurality of springs anchored each at one end to said base plate, lever arms secured to said weights at the pivotally mounted ends, a floating generated calibration plate mounted on said shaft having secured thereto the other ends of said springs, said calibration plate and said levers being position so as to be in substantial juxtaposition to each other and always in contact with each other, and means connecting the free ends of said pivotally mounted weights and said cam plate for normally rotating said cam plate and said cam member in accordance with engine speed.

4; In an ignition distributor for an internal combustion engine having an induction passage, a housing, a shaft mounted through one end of said housing for rotation therein in accordance with engine speed, a base plate mounted on said shaft and disposed normally thereto, a cam member normally rotatable with said shaft for effecting a make and break of the ignition circuit, a cam plate rigidly secured to said cam member, a pluralityof diametrically disposed pivotal support members located within said base plate, weights pivotally mounted on said support members and adapted to have arcuate movement in response to variations in engine speed, a plurality of springs anchored at one end to said base plate, lever arms secured to said weights at the pivotally mounted ends, a floating generated calibration plate mounted on said shaft having secured thereto the other ends of said springs, said calibration plate and said'levers being positioned so as to be in substantial juxtaposition to eachother and always in contact with each other, and means connecting the free ends. of said pivotally mounted weights and said cam plate for both normally rotating said cam plate and said cam member in accordance with engine speed and for rotating said cam member relative to said shaft.

5. In an ignition distributor for an internal combustion engine having an induction passage. a housing, a shaft mounted through one end of said housing for rotation therein in accordance with engine speed, a base member mounted on said shaft and disposed normally thereto, a cam member normally rotatable with said shaft for effecting a make and break of the ignition circuit, a cam plate rigidly secured to said cam member, a plurality of pivotal support members extending from said base member, weights pivotally mounted on said support members and adapted to have movement in response to variations in engine speed, a plurality of springs anchored at one end to said base member, lever arms secured to" said weights at the pivotally mounted ends, a floating calibration plate mounted on said shaft having secured thereto the other ends of said springs, said calibration plate and said levers being positioned so as to be in substantial juxtaposition to each other and always in contact with each other, and

means connecting the free ends of said pivotally mounted weights and said cam plate for both normally rotating said cam plate and said cam member in accordance with engine speed and for rotating said cam member relative to said shaft.

6. In an ignition distributor for an internal combustion 'there1n,'a base 'plat'efmounted on said shaft and disposed normally thereto, a cam member normally rotatable with said sh'aft'for effecting a'make and break of the ignition circuit, a plate'rigidly secured to said cam member, a pluralitybf diametrically disposed pivotal support membefsf extending from said base plate, weights pivotally mounted on said support means and adapted to have arcane movement in response "to variations in engine speed,a plurality of springs each anchored at one end to said base plate, lever arms secured to said weights at the pivotallymounted ends, a floating curve plate mounted on said shaft having securedthereto the other ends ofsaid springs, said curve plate and said levers being so positioned so as to b'e' insubstantial juxtaposition to each other, and always in contactwitheach other, and means Connecting the free ends of said pivotally mounted weights and said plate secured to said member for rotating said plate'and said cam member in accordance with engine speed. i V

7. In an ignition distributor for an internal combustion engine having an induction passage, a shaft adapted to be rotated in accordance with engine speed, a cam normally rotated with said shaft, advance devices for adjusting said cam relative to said shaft in accordance with varia: tions in engine conditions, said advance devices comprising speed responsive centrifugal weights biased by com s m at s s and u res n ve s ma y biased by separate constant rate springs, common means connecting said speed responsive weights and saidvacuurn responsive means to said cam, and floating centrifugal force modifying means interposed between said first mentioned constant rate springs and said speed responsive weights for diminishing saidcentrifugal force to an effective one which increases at the most in a linear fashion with respect to engine speed.

8. In an ignition distributor for an internal combustion engine having an induction passage, a shaft adaptedto be rotated in accordance with engine speed, a cam normally rotated with said shaft, advance devices for adjusting said cam relative to said shaft in accordance with variations in engine conditions, said advance devices comprising speed responsive centrifugal Weights biased by constant rate springs and vacuum responsive means normally biased by separate constant rate springs, common means connecting said speed responsive weights and said vacuum responsive means to said cam, and floating centrifugal force modifying means interposed between said first mentioned constant rate springs and said speed responsive weights for varying the effectiveness of said first mentioned constant rate springs so that the effective resisting force thereof approaches a value which varies as the square of the speed of said shaft.

9. In an ignition distributor for an internal combustion engine having an induction passage, a shaft adapted to be rotated in accordance with engine speed, a cam normally rotated with said shaft, advance devices for adjusting said cam relative to said shaft in accordance with variations in engine conditions, said advance devices comprising speed responsive centrifugal weights biased by constant rate springs and vacuum responsive means normally biased by separate constant rate springs, common motion transmitting means connecting said speed responsive weights and said vacuum responsive means to said cam, and floating centrifugal force modifying means interposed between said first mentioned constant rate springs and said speed responsive weights for modifying the movement of said weights to a rate which is consistent to an advance of said cam which increases at the most in a linear fashion with respect to engine speed.

10. In an ignition distributor for an internal combustion engine having an induction passage, a' drive shaft adapted to be driven in accordance with engine speed, a ca membe coa a with. said shaft and a d o. e

angularly adjustable relative thereto for the purpose of advancing and retarding the ignition, means responsive to changes'in engineoperating conditions for adjusting said cam member, said means including engine speed respong ve and engine vacuum responsive elements, said elements comprising a' transverse member mounted to rotate'with said shaft, arm member's pivotally mounted on said transverse member, speed responsive weight members at the outer ends of said arms, said weight members having said vacuum responsive elements formed therein, said weight members and said vacuum responsive elements both being spring biased and being connected serially to said cam member, said connection including a member mounted on said shaft and having calibrated cam surface for modifying the centrifugal force due to said weight members, said latter member being pivotally mounted on's'aid shaft so as to be readily removable and replaceable with a member having a different cam surface soasto effect a change in speed response calibration.

11. In an ignition distributor for an internal combustion engine having an induction passage, a drive shaft'adapted to be drivenin accordance with engine speed, a cam meniher coaxial with said shaft and adapted to be angularly adjustablerelative thereto for the purpose of advancing and retarding the ignition, means responsive to changes in engine operating conditions for adjusting said cam member, said means including engine speed responsive and engine vacuum responsive elements, said elements comprising a inember'mounted'to rotate with said shaft, speed responsive weight members pivotally mounted on said last named member, said weight members including said vacuum responsive elements formed at the free ends thereof, said weight members and said vacuum responsive elements being separatelyv spring biased and being connected to said cam member in a manner so as to be capable of independent adjustment of said cam member, said connection including a member mounted on said shaft and having a calibrated cam surface for'modifying the centrifugal force due to said weight members, said latter member being pivotally mounted on said shaft so as to be readily removable and replaceable to efiect a change in speed response calibration.

12. In an ignition distributor for an internal combustion enginehaving an induction passage, a drive shaft adapted to be driven in accordance with engine speed, a cam member coaxial with said shaft and adapted to be angular 1y adjustable relative thereto for the purpose of advancing and retarding the ignition, means responsiveto changes in engine operating conditions for' adjusting said c am member, said means including engine speedresponsive and engine vacuum responsive elements, said" elements comprising a cross member mountedto rotate with said shaft, weight members pivotally mounted on' said cross member, said weight members having said" vacuum responsive elements formed at the free ends thereof, said weight members and said vacuum responsive elements both being spring biased and being. connected to said cam member in a manner so as to be capable of independent adjustment of said cam member, the spring bias of said vacuum responsive elements being adjustable, said connection including a member mounted on said shaft and calibrated cam surfaces for modifying the effect of said weights, said latter member being pivotally mounted on said shaft so as to be readily removable and replaceable to effect a change in speed response calibration.

13. In anignition distributor for an internal combustion engine having an induction passage, a drive adapted to be driven in accordance with engine speed, a cam member coaxial with said shaft and adapted'to' be angularly adjustable relative thereto for the purpose of advancing and retarding the ignition, means responsive to changes in engine operating eonditions for adjusting said camrnemher, said means including engine speed respons ve and engine vacuum responsive elements, said vacuum responsive elements including stop means to limit the ign t on advance in response to engine vacuum, said elements comprising a lateral member mounted to rotate with said shaft, weight members pivotally mounted on said lateral member, said weight members having said vacuum responsive elements secured to the free ends thereof, said weight members and said vacuum responsive elements both being spring biased and being connected in series to said cam member in a manner so as to be capable of independent adjustment of said cam member, said connection including a member mounted on said shaft and including calibrated cam surface for modifying the effect of said weights, said latter member being pivotally mounted on said shaft so as to be readily removable and replaceable to effect a change in speed response calibration.

14. In an ignition distributor for an internal combustion engine having an induction passage, a drive shaft adapted to be driven in accordance with engine speed, a cam member coaxial with said shaft and adapted-to be angularly adjustable relative thereto for the purpose of advancing and retarding the ignition, means responsive to changes in engine operating conditions for adjusting said cam member, said means including engine speed responsive i 10 and engine vacuum responsive elements, said elements comprising a transverse member mounted to rotate with said shaft, speed responsive weight members pivotally mounted on said transverse member, said Weight members having said vacuum responsive elements secured to the free ends thereof, said weight members and said vacuum responsive elements both being spring biased and being connected to said cam member in a manner so as to be capable of independent adjustment of said cam member,

said connection including a member mounted on said shaft I and having calibrated cam surface for modifying the effect of said weights, the vacuum connection between said induction passage and vacuum responsive elements being through said shaft and said weight members and including a flexible conduit so as to require only a single rotary vacuum seal at said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 

